Combination of inductances for wireless



,April 13 19 7 1,580;' 509 D. G. LITTLE COMBINATION OF- INDUCTA'NCES FOR WIRELESS Filed June 5', i921 AIM/ WITNESSES: INVENTOR v a I D z/M/(GL/Zf/e ATTORNEY Patented Apr. 13, 1926.

UNITED STATES PATENT OFFICE.

DONALD G. LITTLE, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND SYLVANIA.

I COMBINATION or nvnnc'rancns non wmn'nnss.

Application filed June 3, 1921. Serial No. 474,724.

To all whom may concern:

Be it known that I, DONALD G. LITTLE,

' a citizen of the United States, and a resident of Edgewood'Park, in the-county of Allegheny and State of Pennsylvania, haye invented a new and useful Improvement n Combinations of Inductances for Wireless, of which the following is a specification.

My invention relates to the coupling of vacuum tubes touantenna circuits and, more particularly, it relates to the coupling of vacuum tubes of the feed-back type to antennacircuits in either radio telephony or radio telegraphy. a

One object of my invention is to allow the tuning of the antenna circuit to be varled without changing;- the amount of feed-back voltage induced in the grid circuit by the current in the plate circuit.

A further object of my inventionis to devise a system for the accomplishment of the above outlined'object that shall have but few elements and be simple in construction and manipulation.

In regenerative continuous-wave systems,

it is esential that the feed-back voltage induced in the grid circuit by the current in the plate circuit shall remain constant, within narrow limits, regardless of the wavelength to which the system is tuned. 'Hertofore, it has been impossible to adjust the tuning of such systems with the assurance that the feed-back adjustment will remain correct, and it has been'necessary to' go through a tedious processof testing and experimentation in order to find the value of inductances necessary to give both the correct wave-length and the correct feed-back j adjustment.

In my system, for receiving, I provide an antenna circuit comprising an antenna inductance device formed of two series-connected coils, the relative position of which is v adjustable; This antenna inductance de-, Vice operates as a feed-back coil and is also conductively connected in the grid circuit" circuit of the tube is inductively coupled to the antenna inductance device, and the value of the antenna inductance' device may be varied without altering the voltage of the feed-back connection. 7

In the sending apparatus, an antenna inductance device formed of the two adjustable coils is located within the plate circuitof the tube, and the length of wave transmitted may be varied without varying the voltage induced in a feed-back coil inductively coupled to theantenna'inductance device.

.In the drawings:

Figure 1 is a diagrammatic view of cir- MANUFACTURING COMPANY, A "CORIORATION 0F PENN- cuits and apparatus utilizing the principles of my invention, in which a three-electrode vacuum tube operates as a receiver.

.Fig. 2 is a similar view illustrating a sending system employing a three-electrode vacuum tube having circuits coupledin accordance with my invention.

Fig. 3 is a similar view illustrating a modification;

'In Fig. 1 1s shown-an antenna circuit comprising an antenna 1, a variable condenser 2 and a variometer 3 formed by two coils .4 and 5 connected in series and adjustable in relative position. In practice, the inductance coil 5 is wound on "a small form and is mounted to rotate inside of the coil '4. Thus, the inductance of the variometer 3 may be changed to vary the wave length of the antenna circuit. From the variometer 3 the antenna circuit is connected to ground.

Inductively coupledto the-variometer 3 is a coil 6. In practice, the coils 6 and 4 are preferably wound on the same form and have, therefore, mutual inductance. The coil 6 has, likewise, mutual inductance with the combination 45, which changes forvarious positions of the coil 5. With proper design of the'coils' 4, 5 and '6, the voltage induced in coils .4 and 5 by coil 6 may be maintained substantially constant for all adjustments of the combination 4-5.

A three-electrode receivin bulb 7 having a grid element 8,a plate e ement 9 and a' filament'element 11, has its grid circuit condnctively connected to the antenna-circuit, the leads being taken from op osite sides of the variometer 3. To provlde suitable current to heat the filament 11, I have Shown an .A battery 12. The induction coil 6 is connected in the plate circuit ofthe tube which likewise comprises a plate battery 13 and a telephone receiver 14. 'To

provide a proper by-pass for radio-frequency currents, I have Sl'lOWH a bypass condenser which shunts the telephone receiver 14 and the plate battery 13.

By suitably shaping and proportioning the tuning reactor 2 and the coil 5, having due regard to the coils 4 and 6 and the particular characteristics of induction and capacity of the aerial construction employed, the combinedtuuing variometer and feed-back coil 4, 5, 6 maybe devised in accordance with the design hereinbefore described, whereby the voltage induced inthe variometer 3 by the-currentflowing in the coil 6 may be held vacuum tube of the feed-back type coupled in accordance with the principles of my invention. The antenna circuit comprises an antenna 1 and a variometer 17 corresponding to the variometer 3 of the antenna circuit described in connection with Fig. 1, The

variometer 17 is formed of two coils 18 through a variable condenser and 19 connected in series. The coil 19 may be mounted to rotate within the coil 18 whereby the relative positions of the coils 18and 19 may be changed inorder to vary the effective inductance of the variometer 17. The antenna circuit is connected,

In-inductive relation to the variable inductance device 17 is acoil '22 which is preferably wound on the same form as the coil 18. .There is thus mutual inductance between the coils 18 and 22, as there isllzike wise between the coil 22 and the combination 1819. The mutualinductance between the coil 22 andthe coils 18 and 19 varies for various positions of the coil 19 within the coil 18. The design is such that the voltage induced in the coil 22 by the variometer 17 will be substantially constant for .all adjustments of the variometer 17.

A- three-electrode vacuum tube 23, acting as' an oscillator. and having a plate element 24, a grid element 25 and'a filament element .26, has its plate circuit coupled conductively to the antennacircuit, the leads being taken.

from the antenna end of the variometer 17 and the ground connection. Shunted around the variable condenser 21 of the antenna circuit is a direct-current generator 27 which supplies direct current to the plate circuit of the tube. In the'grid circuit 21, to ground. I

back coupling between the grid and plate circuits. The feed-back voltage induced in the coil 22 of the grid circuit by the plate stantially constant for alladjustments of the variometer 17, The'output of the tube 23, tends to remain constant since the potential induced on the grid 25 remains constant.

In Fig. 3, I have shown a more general solution of the problem, as applied to a receiving circuit. The system shown in Fig. 3 is the same. as that" shown in Fig. 1 except that the tuningcondenser 2 is omitted and the coil 6, instead of being rigidly mounted with respect to the coil 4:, is wound on a separate form 30 which is pivoted at) one end, as at 31. The other end of the form 30 is provided with a pin 32 which rides in the slot 33 of any suitable .cam device 34, the shape of which may bedetermined experimentally. The cam isv pivoted as at 35 current flowing in the variometer 17 is sub- Cir and is mechanically connected to the variometer 3, as indicated schematically by the connecting means 36. .In this manner, the

relative positions of the coil 6 and the variometer 3 may be adjusted simultaneously with the adjustment of the variometer in order .to facilitate the! achievement of the i I substantially constant feed-back. voltage or which my system is designed. v

While I have shown several forms of my invention in the'appended drawings, I do not wish to be restricted thereto but I desire i that only such restrictions shall be placed upon my invention as are set forth in the appended claims.

I claim as my invention i r 1. In a radiodevioe, a re eneratively connected vacuum tube, inclu ing a reactor in the grid circuit, a reactor. in the plate circuit coupledthereto, ineans for adjusti each of the said reactors independently, aiid means mechanically associated with one of said adjusting means for adjusting the relative position of said reactors when the associated adjusting means. is actuated, to, thereby vary the coupling between said reactors when vaned.

'2., Ina radio devlce, a re eneratively connected vacuum tube, inclu ing a reactor in the reactance'of one of them is the grid circuit, areactor in the plate circuit coupled thereto, means for ad usting each of thesai'd reactors independently, and means mechanically associated with one of said adjusting means and including a cam for adjusting the relative position of said reactors when the associated adj ustin means is actuated to therebyvary the coup 'ng betweensaid reactors when the reactance of one of them is varied, said cam being so Shaped that the coupling corresponding to each. value of said'reactance is optimum.-

3; In a radio-receiving set an antenna 5 circuit including avariometer, a regenerative vice, an. adjustable inductor in the plate circuit of said vacuum-tube device coupled to said variometer, said coupling constitut I ing the feed-back of said regenerative vacuum-tube device, means for varying the position of said indicator relative to said variometer, to thereby vary. the feed-back coupling and means mechanically actuated by said inductor for controlling said positionvarying means.

In testimony whereof, I have" hereunto subscribed my name'this 31st day of May, 1921.

/ DONALD G. LITTLE. 

